Allow returns/expects to be expressed in terms of a media type; what about multiple types?

[lanthaler]

This is, e.g., necessary for things such as images. It is also necessary to define how multiple types in expects/returns should be interpreted. Do requests/responses need to be instances of all classes or just of at least one?

[vanthome]

schema.org has for its hydra:expects counterpart corresponding properties for media types of the input and output schema:encodingType and schema:contentType.
One could define multiple operations, one per type, if the content types would differ per @type.
At lease for the input part I think there should be a corresponding concept in hydra.
For the output it can make sense for documentation purposes (we had a similar discussion already I remember).

[alien-mcl]

This should be covered by the PR #186 - closing